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Electrocatalytic reduction of carbon dioxide (CO2RR) to C2+ products presents an ideal approach to mitigate the continuous accumulation of CO2 for achieving carbon neutrality. However, the selectivity for C2+ products is constrained by the high energy barrier associated with C–C coupling and the sluggishness of multiple proton-coupled electron transfer (PCET), resulting in reduced efficiency and selectivity. Herein, a single-atom Cu catalyst with second-shell S coordination (Cu–C3N4–S) is prepared, exhibiting higher ethylene (C2H4) faradaic efficiency (60.2% at −0.9 V vs. RHE). The second-shell S doping structure is confirmed using a DFT theoretical model combined with synchrotron X-ray absorption spectroscopy. Simultaneously, the adsorption of *CO2 intermediates is detected by in situ Raman spectroscopy, allowing for the inference of potential reaction pathways. It is confirmed that through the regulation of second-shell S doping, a notable reduction in the energy barrier of C–C coupling ensues, concurrently tackling the electron demand in the PECT reaction via the construction of an electron transfer pathway (S–N–Cu) at a lower overpotential. This study contributes novel insights to the design of atomic-sized copper-based catalysts inspired by the indirect coordination and heteroatom regulation technique. [ABSTRACT FROM AUTHOR]

A strategy involving organic photocatalytic conversion using hydrothermal synthesis of high-entropy oxide (HEO) (CoCuZnMnNa)Ox nanoparticles was developed. Under mild conditions, HEO nanoparticles were driven by visible light to achieve ideal yields and selectivity in sulfide oxidative coupling reactions and benzimidazole cyclization reactions, with a wide substrate range. This study is expected to contribute to the use of high-entropy oxides in organic photocatalysis. [ABSTRACT FROM AUTHOR]

Recently, the increasing concerns regarding environmental and energy-related issues due to the use of fossil fuels have triggered extensive research on sustainable electrochemical energy storage and conversion (EESC). In this case, covalent triazine frameworks (CTFs) possess a large surface area, tailorable conjugated structures, electron donating–accepting/conducting moieties, and excellent chemical and thermal stabilities. These merits make them leading candidates for EESC. However, their poor electrical conductivity impedes electron and ion conduction, leading to unsatisfactory electrochemical performances, which limit their commercial applications. Thus, to overcome these challenges, CTF-based nanocomposites and their derivatives such as heteroatom-doped porous carbons, which inherit most of the merits of pristine CTFs, lead to excellent performances in the field of EESC. In this review, initially, we briefly highlight the existing strategies for the synthesis of CTFs with application-targeted properties. Next, we review the contemporary progress of CTFs and their derivatives related to electrochemical energy storage (supercapacitors, alkali-ion batteries, lithium–sulfur batteries, etc.) and conversion (oxygen reduction/evolution reaction, hydrogen evolution reaction, carbon dioxide reduction reaction, etc.). Finally, we discuss perspectives on current challenges and recommendations for the further development of CTF-based nanomaterials in burgeoning EESC research. [ABSTRACT FROM AUTHOR]

The effective and highly selective aerobic oxidation of sulfides to sulfoxides under green and mild conditions is still an important but challenging process. Here we present a photocatalytic system for sulfide oxidation to sulfoxides with high yields under blue LED irradiation. The photo-oxidation was carried out in water with oxygen over a bismuth-rich catalyst of Bi4O5Br2. The apparent quantum efficiency of sulfide oxidation reached 57.4%. The developed system provided a simple, robust, green and sustainable promising candidate for the practical application of sulfide oxidation. [ABSTRACT FROM AUTHOR]

Nickel element cannot exist stably on its own, but with an bared of an NiO shell, nickel element can realize desirable stable existence. Herein, Ni2+ was photoreduced to Ni particles and deposited on graphite carbon nitride (g-C3N4) under vacuum. The surface of Ni particles was oxidized to form an NiO shell after the samples were exposed to air, and elemental Ni was protected by the encapsulation of the NiO shell to realize the coexistence of Ni and NiO. The chainmail co-catalyst of NiO shell-encapsulated Ni over g-C3N4 (Ni/NiO/g-C3N4) was prepared and applied in the photocatalytic reduction of CO2 and showed the best photocatalytic activity when the Ni/NiO loading was 3 wt%. After illumination for 2 h, the CO generation rate reached a value of 27.9 μmol g−1 h−1, which was about nine times that of pure g-C3N4. The steady-state surface photovoltage spectrum (SPV), ultrafast spectrum of transient photovoltage (TPV) and time-resolved photoluminescence (PL) spectra as well as electrochemical tests showed that Ni/NiO/g-C3N4 has a low recombination rate of photogenerated electron–hole pairs. In situ Fourier transform infrared spectroscopy (FT-IR) and DFT calculations were used to explain the photocatalytic mechanism at the molecular level. [ABSTRACT FROM AUTHOR]

Photocatalytic conversion of CO2 to solar fuels is considered an alternative approach for simultaneously mitigating the greenhouse effect and solving energy shortage. The efficient light harvesting and the thermochemical conversion have been demanding quests in photocatalysis due to the relatively low solar energy utilization efficiency. In this work, oxygen vacancies are induced in MoO3 for improving photo-thermal CO2 reduction efficiency by capturing near-infrared (NIR) photons. The localized surface plasmon resonance (LSPR) of MoO3−x triggered by oxygen vacancies enables the efficient capture of NIR photons. Additionally, oxygen vacancies can promote the carrier separation, improve CO2 adsorption on the defective surface and lower the barrier of CO2 hydrogenation during the conversion process. As a result, MoO3−x displayed dramatically enhanced photo-thermal synergistic CO2 reduction under simulated sunlight (UV-Vis-IR) irradiation than MoO3. The amount of CO produced by MoO3−x can reach 10.3 μmol g−1 h−1, which is 20 times higher than that of MoO3 (0.52 μmol g−1 h−1). And the CH4 production of MoO3−x can reach 2.08 μmol g−1 h−1, which is 52 times higher than that of MoO3 (0.04 μmol g−1 h−1). In situ FT-IR and theoretical calculations also proved the enhanced activity of MoO3−x. This work highlights the significance of defect engineering for improving the photo-thermal catalytic conversion of CO2. [ABSTRACT FROM AUTHOR]

Oxygen defective yolk–shell BiO2−x spheres are successfully synthesized by a facile solvothermal method for the first time. The variations between the diffusion rate of the core and the formation rate of the shell, which are caused by the temperature gradient originating from the heating rate, result in the formation of BiO2−x spheres with different interior structures. The as-synthesized yolk–shell BiO2−x spheres possess distinctive oxygen vacancies, which are demonstrated by electron paramagnetic resonance and X-ray photoelectron spectral analyses. The oxygen vacancies with a high affinity for molecular oxygen, and the enhanced light absorption ability resulting from the multiple reflections of the incident light within the interior voids, play key roles in the photocatalytic bacterial inactivation. Scavenger studies indicate that O2− and H2O2 are the major reactive species guaranteeing the prominent oxidation ability toward the bacterial cells. This study would not only provide direct evidence for the oxygen vacancy promoted photocatalytic bacterial inactivation, but also shed light on the design of highly efficient photocatalysts with intricate yolk–shell structures. [ABSTRACT FROM AUTHOR]

Layered bismuth oxychloride (BOC) exhibits highly efficient activity for photocatalytic environmental remediation due to the confinement effect induced excitonic photocatalytic process. However, the strong excitonic process suppresses catalytic reactions with photo-induced electrons, such as hydrogen generation, CO2 conversion and nitrogen fixation. Moreover, the wide band gap of BiOCl limits its application under visible light. In this study, flexible BiOCl nanosheets with oxygen vacancies (BOC-OV) were successfully prepared. Molecular oxygen activation, electronic spin resonance (ESR), transient photocurrent, transient absorption spectroscopy, and transient fluorescence spectroscopy indicated that oxygen vacancies induced exciton dissociation of flexible BiOCl nanosheets. Moreover, oxygen vacancies induced wide spectrum (UV-Vis) absorption. The enhanced exciton dissociation resulted in the superior CO2 conversion of BOC-OV under UV-Vis light irradiation, where the light to carbon monoxide (LTCO) conversion efficiency reached up to 26.5 × 10−6. Theoretical calculations and in situ Fourier transform infrared spectrometry (FT-IR) analysis revealed that the mechanism of oxygen vacancies improves the photocatalytic CO2 conversion with BOC-OV via the CO2 hydrogenation pathway. This study indicates that oxygen vacancies have a great influence on photocatalytic CO2 reduction due to their special surface and electron structure properties. [ABSTRACT FROM AUTHOR]

Co-catalysts and sacrificing reagents are important components in artificial photocatalytic processes. Here we demonstrate that noble-metal loading reverses the temperature dependent photocatalytic activity trends of photocatalytic hydrogen (H2) generation with methanol as a sacrificing reagent. This finding suggested that visible and infrared light can enhance photocatalytic H2 generation via a heat effect over noble-metal/photocatalysts. [ABSTRACT FROM AUTHOR]

In this paper, BiOI@(BiO)2CO3 facet coupling heterostructures were synthesized via exfoliation and ion exchange, and characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and valence-band XPS spectra. With the reaction time increasing, more BiOI can be transformed to (BiO)2CO3, and BiOI@(BiO)2CO3 facet coupling heterostructures were obtained. The photocatalytic results showed that BiOI@(BiO)2CO3 displays much higher photocatalytic activity than BiOI and (BiO)2CO3 under visible-light. The photocatalytic mechanism study revealed that BiOI@(BiO)2CO3 has strong adsorption for RhB molecules due to the ultrathin nanosheets and higher BET, and displays better separation efficiency of photoinduced charge carriers and higher photocurrent due to the {001}/{001} facet coupling. [ABSTRACT FROM AUTHOR]

We firstly demonstrate the opposite photocatalytic activity orders of low-index facets of anatase TiO2 in the liquid phase for rhodamine B (RhB) photocatalytic degradation and in the gaseous phase for the photoreduction of CO2 to CH4. The photocatalytic activity order in the liquid phase for RhB photocatalytic degradation is revealed as {001} ＞ {101} ＞ {010}, whereas the photocatalytic activity order {010} ＞ {101} ＞ {001} is found in the gaseous phase for the photoreduction of CO2 to CH4. The atomic arrangement of the different facets, UV-vis diffuse reflectance spectra, photoluminescence spectra and attenuated total reflectance Fourier transform infrared spectroscopy analysis show that the photoactivity order in the gas phase for the photoreduction of CO2 to CH4 mainly depends on the CO2 molecule adsorption properties on the different exposed facets, and the separation efficiency of the photo-generated carriers determines the photoactivity order for the dye degradation reaction in the liquid phase. These findings also provide a new direction to design efficient photocatalysts and the tuning of their photoreactivity for environmental and energy applications. [ABSTRACT FROM AUTHOR]

Anatase TiO2 nanocrystals with {101}, {001} or {010} single facets of 90% level exposure were controllably synthesized from potassium titanate (PT) without fluorine and organic capping surfactants, and characterized by X-ray diffraction patterns (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and fast Fourier transformation (FFT). The liquid-phase photocatalytic reduction (O2Ṗ− generation) and oxidation (ṖOH generation) activity orders of anatase TiO2 facets are {001} ＞ {101} ＞ {010} upon removing facet synergetic effect and surface fluorine effect. UV-vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra showed that absorbance edge order, and separation efficiency order of photoexcited holes and electrons are {001} ＞ {101} ＞ {010}, which explains the photocatalytic activity order well together with the atomic arrangement of different facets. [ABSTRACT FROM AUTHOR]

Charge separation is very important for increasing the activity of semiconductor-based photocatalysts. Here we show that the main active species of BiOI are photo-induced holes, rather than ṖOH and O2Ṗ−, under visible light irradiation. Based on this finding, the cocatalyst MnOx was used to enhance the transfer of the photo-induced holes, resulting in much higher photocatalytic activity, compared with the photocatalyst without MnOx. MnOx–BiOI heterogeneous nanostructure photocatalysts have been prepared by photo-deposition in Mn(NO3)2 solution, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectroscopy. As-prepared MnOx–BiOI exhibited higher photoactivity than BiOI and Pt–BiOI for the degradation of Rhodamine B (RhB) dye under visible light irradiation. The PL spectrum showed that MnOx enhances the separation efficiency of the photo-induced electrons and holes of BiOI. Finally, BiOI was selectively combined with a deriving-hole-type cocatalyst to enhance the photocatalytic activity, and the reason for the cocatalyst selectivity is also discussed. This finding may be useful in bismuth-based photocatalysts to construct highly efficient solar energy conversion systems. [ABSTRACT FROM AUTHOR]

Highly symmetrical BiOI single-crystal nanosheets (BiOI SCNs) with dominant exposed {001} facets (up to 95%) have been synthesized by annealing BiI3and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, fast-Fourier transform pattern, UV-vis diffuse reflectance and photoluminescence. The thickness and the {001} facets percentage of BiOI SCNs can be tuned by changing the annealing temperature. The thermal decomposition process of BiI3and the formation mechanism of BiOI SCNs were investigated. BiOI SCNs exhibit higher photoactivity (about 7 times) than irregular BiOI for degradation of Rhodamine B (RhB) dye under visible light irradiation. The {001} facets are the reactive facets of BiOI. The origin of {001} facets-dependent photoactivity is due to an improvement of the separation efficiency of photo-induced electrons and holes. [ABSTRACT FROM AUTHOR]

The effective and highly selective aerobic oxidation of sulfides to sulfoxides under green and mild conditions is still an important but challenging process. Here we present a photocatalytic system for sulfide oxidation to sulfoxides with high yields under blue LED irradiation. The photo-oxidation was carried out in water with oxygen over a bismuth-rich catalyst of Bi4O5Br2. The apparent quantum efficiency of sulfide oxidation reached 57.4%. The developed system provided a simple, robust, green and sustainable promising candidate for the practical application of sulfide oxidation. [ABSTRACT FROM AUTHOR]

In this paper, BiOI@(BiO)2CO3 facet coupling heterostructures were synthesized via exfoliation and ion exchange, and characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and valence-band XPS spectra. With the reaction time increasing, more BiOI can be transformed to (BiO)2CO3, and BiOI@(BiO)2CO3 facet coupling heterostructures were obtained. The photocatalytic results showed that BiOI@(BiO)2CO3 displays much higher photocatalytic activity than BiOI and (BiO)2CO3 under visible-light. The photocatalytic mechanism study revealed that BiOI@(BiO)2CO3 has strong adsorption for RhB molecules due to the ultrathin nanosheets and higher BET, and displays better separation efficiency of photoinduced charge carriers and higher photocurrent due to the {001}/{001} facet coupling.

We firstly demonstrate the opposite photocatalytic activity orders of low-index facets of anatase TiO2 in the liquid phase for rhodamine B (RhB) photocatalytic degradation and in the gaseous phase for the photoreduction of CO2 to CH4. The photocatalytic activity order in the liquid phase for RhB photocatalytic degradation is revealed as {001} > {101} > {010}, whereas the photocatalytic activity order {010} > {101} > {001} is found in the gaseous phase for the photoreduction of CO2 to CH4. The atomic arrangement of the different facets, UV-vis diffuse reflectance spectra, photoluminescence spectra and attenuated total reflectance Fourier transform infrared spectroscopy analysis show that the photoactivity order in the gas phase for the photoreduction of CO2 to CH4 mainly depends on the CO2 molecule adsorption properties on the different exposed facets, and the separation efficiency of the photo-generated carriers determines the photoactivity order for the dye degradation reaction in the liquid phase. These findings also provide a new direction to design efficient photocatalysts and the tuning of their photoreactivity for environmental and energy applications.

Black BiOCl with oxygen vacancies was prepared by UV light irradiation with Ar blowing. The as-prepared black BiOCl sample showed 20 times higher visible light photocatalytic activity than white BiOCl for RhB degradation. The trapping experiment showed that the superoxide radical (O(2)(•-)) and holes (h(+)) were the main active species in aqueous solution under visible light irradiation.

BiOCl nanosheets (BiOCl NSs) were synthesized by hydrolyzing a hierarchical flowerlike molecular precursor (Bi(n)(Tu)(x)Cl(3n), Tu = thiourea). High photoactivity of {001} facets of BiOCl NSs was observed, and the mechanism was discussed., (This journal is © The Royal Society of Chemistry 2011)